Tailored sheet metal blanks conventionally consist of two or more metal sheets of equal or unequal thickness welded together along linear weld seams. As compared to sheet metal blanks of uniform thickness, tailored blanks have the advantage that the designer can more closely match the strength, ductility, corrosion resistance or other features to the requirements of a part design. For example, the designer can provide additional strength where required in portions of a stamped part, while minimizing the overall material used in other portions.
Tailored sheet metal blanks have conventionally been assembled, welded, processed and handled in individual stand-alone work stations.
For example, in a conventional processing operation, coils of sheet metal are slit and shear cut to component sizes and stacked. The component stacks are then transferred to a welding station, where they are welded together and the output weldments are restacked. If the linear weld seams are to be ground flush, the weldment stack is transferred to a grinding station where each weldment is handled again, ground, and restacked. For other operations, such as oiling the weld seam (for corrosion resistance), or dimpling the sheet metal weldments (to aid stacking of the stamped parts) individual stations and repetitive handling are conventionally required.
Significant inefficiencies result from the repeated handling and restacking involved in conventional manufacture of tailored blanks. The use of stand-alone work stations for each operation likely has evolved from the gradual increase in acceptance of tailored blank technology.
By introducing further and further improved steps in manufacture, the designer can optimize the final end use of the tailored blank. However, such increasing number of steps has created a demand for an integrated method of manufacture.
Since it may be necessary to form a dimple at any location on a blank of any shape or size within the maximum design, conventionally dimpling is performed in a large punch press which is sized to accomodate the entire maximum blank size. Such dies and presses are extremely large and expensive but have heretofore been considered necessary due to the size of blanks and the need to select a wide variety of dimple locations.
The use of conventional methods has the advantage that it is easily adapted to manufacture the widely varying sizes and configurations of weldments encountered in automobile part production for example. The use of individual operations allows flexibility in output and part design which counteracts the disadvantages of repeated handling described above.
Therefore, it is desirable to provide an integrated method and apparatus for manufacturing tailored blanks, which can accomodate a wide variety of weldment configurations and sizes. However, such a system must also be rapidly adapted to produce different parts to be economically feasible. Rapid changeover is especially essential with the widespread adoption of just-in-time manufacturing which does not allow for long production runs and the economies of scale conventionally encountered in sheet metal part production.